While Pratt looks fitter than ever, he said the best part of his shocking health transformation is having more energy.

“I really just kind of cleaned up my diet and my life — it really just changed everything for me,” Pratt told Esquire. "I like clothes now. I have more energy. I sleep better. My sex drive is up."

Pratt, 35, raised eyebrows last summer after showing off his dramatic weight loss on Instagram after following a low carb, beer-free Paleo-style diet for six months. At the time, Chris had been training to play Peter Quill in the action flick, "Guardians of the Galaxy."

Pratt said becoming ripped took a lot of dedication but was worth the effort. "You have to eat protein," he said. "You can't have hash browns, or burgers, or anything fried. You can't have carbs. You have to work out five times a week."

"I did a training for a triathlon in terms of swimming, biking, running," Chris told Greggenheim. "I also did weights and CrossFit high-intensity interval training, jogging and straight body-building: Pull ups, push ups, P90X. I did about four hours a day for maybe five months."

P90X, the cross-training workout created by fitness expert Tony Horton, has a huge celebrity following, including Pink and legendary rocker Bruce Springsteen.

Pratt is no stranger to major weight fluctuations. In 2011, Pratt lost 30 pounds for the drama "Moneyball" and then, shortly afterward, regained 50 to 60 pounds for the comedy "Ten Year."

"I went from 220 pounds that I cut down for 'Moneyball' to almost 270-280 pounds for 'Ten Year,' " he told Conan O'Brien in 2012. "I gained like 50 pounds to play this fat, alcoholic character. I would drink dark beer every night."

At some point in between, Pratt got super-buff to play a Navy SEAL in the 2012 drama, "Zero Dark Thirty." After that film wrapped, Chris gained 60 pounds in four months to play an obese lawyer in the comedy "Delivery Man." His weight has fluctuated since then.

Tim McGraw Lost 40 Pounds With Paleo and CrossFit

Pratt said he did not have a weight problem growing up but allowed himself to be overweight for the past seven or eight years. In addition to looking bad, Chris said being obese made him very depressed.

"I do know what it feels like to eat emotionally," Pratt said. "To be sad and make yourself happy with food, and then be almost immediately sad again, and then ashamed."

Now a father (Chris has a two-year-old son with actress Anna Faris), Pratt said he feels better than ever and has totally embraced a healthier lifestyle. "Blood's flowing," he said. "I'm less susceptible to impulse. I'm in a different mode."

Pratt isn't the only celebrity who has transformed his body with the low-carb Paleo diet and CrossFit. Country superstar Tim McGraw attributed his incredible 40-pound weight loss to CrossFit and Paleo. Similarly, Joe Manganiello maintains his rippling physique with CrossFit and Paleo.

Actress Megan Fox said she lost all her baby weight on a strict low carb, alcohol-free, dairy-free Paleo-inspired diet, and Kristin Cavallari credited the Paleo diet for her 20-pound weight loss just three months after giving birth to her second child.

Share this article

Samantha Chang is the co-owner of www.theimproper.com., an arts and entertainment website in New York City. A graduate of the University of Pennsylvania, Samantha enjoys running, cycling and taking photos. Contact her at schang@theImproper.com.